Utilities and other entities operate distribution systems for water, gas, and electricity to deliver these resources to various consumers connected to the distribution system. Typically, each consuming entity has at least one meter measuring the amount of the resource that it is removing from the distribution system. The utility likewise measures the amount of the resource that it is supplying to the distribution system, either through supply meters or other similar means. In a perfect world, the total amount of the resource supplied should equal the amount consumed.
This, however, is not a perfect world. Utilities commonly encounter discrepancies between the amount supplied and the amount consumed in their distribution systems. These discrepancies may usually be attributable to one or more of the following factors: inaccuracies in metering devices; leaks; line breakages and known singular events such as a fire crew accessing water from a hydrant to put out a fire; and theft. The difference between the measured quantity of resource supplied and the measured quantity of resource consumed is simply referred to as “unaccounted for.”
Except for known events such fires and reported line breakages, utilities traditionally have had a difficult time accurately measuring the amount of unaccounted for resources, monitoring changes in the amount over time, and therefore being able to identify the source and cause of missing resources. This is because distribution systems usually include large numbers of meters, and with meters that must be read manually, it was impractical to gather a series of readings from such a large number of meters in a short time as is necessary to accurately measure and monitor the unaccounted for resource.
More recently, metering systems have utilized wireless communications modules operatively connected to the meter itself, such that the communications module could report the meter reading electronically to a communications network. Such networks initially utilized a mobile communications device that a utility worker would use to more rapidly collect readings as he drove within range of the meters. Later, the networks include stationary receivers designed to receive messages from a designated set of meters with a certain range, or the communications modules on the meters are capable of communicating with each other and passing messages along to a module connected that is connected to a gateway to the larger network. Various network topologies and technologies exist in the prior art for transmitting meter readings from a communications module at the meter to a central data collection or processing unit. In these systems, the communications module at the meter might transmit a reading on a predetermined interval (a “bubble up” system), or the module might respond to a command to report a meter reading from the central host or a nearby receiver or collector. Such networks are known and understood by those of ordinary skill in the art and will not be discussed in further detail here. In any case, such communication systems offer the ability for near instantaneous transmission of meter readings from the meter itself back to the central host computer for compilation and analysis.
In a large distribution network, however, a significant number of readings will be missing because of meters with inoperable or unresponsive communications modules, or where the signal was otherwise blocked, corrupted, or lost in transmission. These missing readings compromise the ability to measure and monitor the amount of an unaccounted for resource, even with a wireless communications network. In addition, to determine consumption, including to measure the amount of an unaccounted for resource, the utility usually must obtain readings for a large number of meters over a specific time period, such as a 24-hour period. Many meters make readings on regular intervals determined by internal clocks, which are not necessarily synchronized with an actual time. Therefore, while a meter may make a reading on a regular interval, such as every 15 minutes, or hourly, those intervals may fall randomly on the actual clock. For example, a meter taking a reading every 15 minutes may take those readings at 11, 26, 41, and 56 minutes after the hour. Moreover, meters in a distribution system may not be synchronized with one another; so even if all are taking a reading on the same reading interval (e.g., every 15 minutes) the distribution of when those readings are made, with respect to actual time, is somewhat random. Also, the internal clocks of meters may be subject to drift in accuracy over time, such that synchronization or lack thereof, with respect to actual time, may be constantly changing. For all of these reasons, the readings taken by meters are usually out of synch with one another and with defined points on the clock (such as the top of every hour). As a result, an actual reading at the desired beginning and ending of the specified time period (such as midnight), will likely be missing for a large number of meters. With a complete set of readings for a defined time period, a utility can determine if the unaccounted for resource is due to leaks, inaccuracies in meters, or theft.
Thus, there is a need for a method and system to provide a utility or other entity a complete set of readings for each meter of interest in a large distribution system, in which some meters may be inoperable, nonresponsive, where data transmissions may be lost or corrupted, and where lack of synchronization results in readings being missing for a defined time period.